1. Field of the Invention
The present invention relates to a device employed for ventilating a patient during surgical use of a laser in a patient's airway.
2. Description of the Background Art
Endotracheal tubes for controlling ventilation of a patient during surgery are known in the art. Such devices generally include a tubular body for conveying the ventilation and anesthesia gases to and from a patient's lungs. In order to provide a tight seal with the trachea for controlled ventilation, a balloon or cuff typically is provided near a distal end of the endotracheal tube, the cuff being inflatable from outside the patient by means of an auxiliary conduit. In order to minimize the possibility of damaging a respiratory tract into which a ventilation device is inserted, such devices usually are constructed of flexible polymeric material.
Laser microlaryngeal surgery is increasingly being employed for treatment of localized laryngeal and tracheal lesions. There are several known types of surgical lasers, including ruby, argon, helium-neon Nd-YAG and carbon dioxide lasers. However, the carbon dioxide laser appears best for the removal of laryngeal papillomas, polyps, nodules, cysts and the like, since carbon dioxide lasers produce 10.6.mu. lightwaves which are absorbed by biological tissue, destroying targeted cell membranes and vaporizing cellular contents.
During laser microlaryngeal surgery, an unobstructed, binocular view of a lesion is provided. This provides advantages over other known types of laryngeal surgery, such as diathermy and cryosurgery, which utilize a probe that may obscure a surgeon's view of the operative field. In addition, lasers provide a relatively bloodless field, and post-operative edema is usually absent because the area treated by laser is sharply defined. Ideally, laser surgery leaves the surrounding tissue totally unaffected, allowing rapid healing with minimal post-operative scarring.
One consideration of microlaryngeal surgery is that the operative field is shared by the anesthesiologist and the surgeon. This can be addressed by using an endotracheal tube having an outer diameter sufficiently small to permit the surgery to take place while having an inflatable cuff large enough to make a seal. Alternatively, the surgery can occur with no tube in the airway with patient ventilation and anesthetic gas delivery given during interruptions in surgery via a mask.
There are disadvantages to having no tube in the airway. These include: lack of complete airway control, the possibility of apnea or hypoventilation with secondary cardiac arrythmias, laryngospasm from too light a plane of anesthesia, non-immobilized vocal cords, and exhalation of potent anesthetic gases through the open mouth of the patient making scavenging of these gases difficult.
Although performing microlaryngeal surgery with no tube in the airway is undesirable for reasons listed above, problems also arise during laser microlaryngeal surgery when employing an endotracheal tube. These problems typically involve damage caused by the laser of one or both of the endotracheal tube and inflatable cuff. Laser damage to the ventilation device may result in loss of airway management, burning of respiratory tissue, and the production of toxic fumes.
One method which has been proposed to reduce the risk of damaging the endotracheal tube during laser surgery is to wrap the endotracheal tube with metallic tape. However, wrapping a tube in metal tape is time consuming, and rough edges of the tape may abrade and injure the mucosa of the pharynx and larynx. In the event of a poor wrapping job, the possibility exists that uncovered areas can be ignited, as does the possibility that loose pieces of tape can be aspirated. Wrapped metal tape increases the possibility of a kink developing in the tube, and inadvertent mucosal damage may occur due to reflection of the laser beam off the tape.
Another proposed method for reducing the risk of ignition of an endotracheal tube is to wrap the tube in wet muslin. However, this also is time consuming, and the muslin adds additional bulk to the tube. Additionally, the muslin may dry out and ignite during surgery.
Yet another proposed method for reducing the risk of ignition of an endotracheal tube is to coat the tube with dental acrylic. However, dental acrylic rigidifies the tube and is not completely impenetrable by surgical lasers. The dental acryic further adds undesired bulk to the tube and is time consuming to apply.
Metal tracheal tubes also have been utilized to avoid ignition of the tube during laser surgery, but problems with the use of metal tracheal tubes have been encountered. These problems include tissue damage brought about by insertion of rigid metal tubes, and inadvertent mucosal damages due to reflection of the laser beam off of the metal tube. Metal tracheal tubes typically have large external diameters which precludes their use with pediatric patients and patients with tracheal stenosis, and generally have no inflatable cuff for creating an air-tight seal. Moreover, the curently available flexible metal tracheal tubes typically are constructed such that the wall of the tube is not air tight.
Venturi ventilation has been employed during laser microlaryngeal surgery, but this may pose problems such as pneumothorax, pneumomediastinum, stomach inflation, aspiration of secretions, complete respiratory obstruction, and dehydration of mucosal surfaces.
The use of metallically filled polymers for tube construction also has been suggested to reduce the risk of ignition of endotracheal tubes. However, proposed metallically filled polymers provide only minimal resistance to penetration by laser beam impact (especially in O.sub.2 /NO.sub.2 enriched atmospheres), and are generally quite expensive.
There remains a need in the art for a surgical ventilation device which is resistant to laser-caused dysfunction during laser surgery.